2008 St. Johns County, FL Countywide Lidar

Airborne terrestrial LiDAR was collected for St. Johns County, FL. System Parameters/Flight
Plan. The LiDAR system acquisition parameters were developed based on a maximum average
ground sample distance of 2.1 feet. A Leica ALS50 LiDAR sensor was used for acquisition.
Acquisition specifications for the sensor follows: Field of View (full angle) - 24
degrees, Nominal flight altitude (AGL) - 3000 feet, Airspeed - 130 mph (113 knots),
Laser pulse rate - 100,000 Hz, Nominal swath width (on ground) - 1275 feet, Maximum
cross track point spacing - 2.07 feet, Maximum along track point spacing - 4.30 feet,
Average point spacing - 1.67 feet, Flight line spacing - 970.47 feet, Side overlap
- 23.91 percent. LiDAR System Calibration. Prior to the LiDAR acquisition, the system
underwent a calibration to verify the operational accuracy and misalignment angles.
Boresight calibrations were performed for the LiDAR system at the beginning and end
of each flight mission. LiDAR Data Acquisition. LiDAR data acquisition only occurred
when the sky was sufficiently clear of clouds, smoke, and atmospheric haze. The LiDAR
data was processed immediately after the acquisition to verify the coverage had no
voids. GPS/Inertial Measurement Unit (IMU) Post Processing. The GPS and IMU data was
post processed using differential and kalman filter algorithms to derive a best estimate
of trajectory. The quality of the solution was verified to be consistent with the
accuracy requirements of the project. LiDAR Processing and Classification. The LiDAR
data was post processed and verified to be consistent with the project requirements
in terms of post spacing and absence of artifacts. The point cloud underwent classification
to determine bare-earth points (class 2), noise points (class 7), water returns (class
9), and unclassified data (class 1). Class 12 contains LiDAR points removed from the
overlap region between adjacent flight lines.

DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National
Oceanic and Atmospheric Administration, U.S. Department of Commerce

Originator

St. Johns County, FL GIS Division

Publisher

Publisher information not available.

Date(s)

publication: 2009-01-06

Data Presentation Form:

Digital image

Dataset Progress Status

Complete

Data Update Frequency:

As needed

Supplemental Information:

Project Title- Countywide Digital Contour Mapping; Vendor Name- Woolpert, Inc. The
Final QA/QC Quantitative Assessment Report for this data set may be viewed at: ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/fl/st_johns/2008_StJohns_MTS_Final_Report_Lidar_Ortho.pdf
The Final Ground Control Survey Report (more detail given to field activities, process,
etc.) may be viewed at: ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/fl/st_johns/2008_StJohns_MTS_Final_Report_Ground_Control.pdf
An additional Aerial Triangulation Report may be accessed at: ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/fl/st_johns/2008_StJohns_MTS_Final_Report_AerialTriangulation.pdf

Purpose:

The DTM was developed to support the development and maintenance of the St. Johns
County Countywide Digital Contour Mapping Project.

Use Limitations

These data depict the elevations at the time of the survey and are only accurate for
that time. Users should be aware that temporal changes may have occurred
since this data set was collected and some parts of this data may no longer represent
actual surface conditions. Users should not use this data for critical
applications without a full awareness of its limitations. Any conclusions drawn
from analysis of this information are not the responsibility of NOAA or any of its
partners. These data are NOT to be used for navigational purposes.

Time Period:

2008-02-14 2008-02-19 to 2008-02-17 2008-02-21

Spatial Reference System:

urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters

Spatial Bounding Box Coordinates:

N: 30.253509

S: 29.621834

E: -81.212177

W: -81.669741

Spatial Coverage Map:

Themes

Bathymetry/Topography

lidar

Digital Elevation Model

DEM

remote sensing

topography

Places

US

Florida

St. Johns County

Use Constraints

No constraint information available

Fees

Fee information not available.

Lineage Statement

Lineage statement not available.

Processor

Woolpert, Inc.

DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National
Oceanic and Atmospheric Administration, U.S. Department of Commerce

Ground (class 2) LAS points were extracted in ArcMap, using a Woolpert Team-developed
VB Script, and loaded into the MASSPOINTS feature class for each area's Geodatabase
as multipoint geometry.

The NOAA Coastal Services Center received the data in LAS format. The files contained
Lidar elevation and intensity measurements. The data were projected in State Plane
coordinates (NAD83; Florida East) and referenced to the North American Vertical Datum
of 1988 (NAVD88) using the Geoid03 model. The following processes were performed to
make the data available within the Digital Coast: 1. The data were converted from
state plane (NAD83; Florida East) to geographic coordinates (NAD83). 2. The data were
converted from NAVD88 (orthometric) heights to GRS80 (ellipsoidal) heights using the
Geoid03 model. 3. The LAS data were sorted by latitude and the headers were updated.

The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp
transfer from the NOAA Coastal Services Center. The data are
currently being served via NOAA CSC Digital Coast at http://www.csc.noaa.gov/digitalcoast/.
The data can be used to re-populate the system. The data are archived in LAS
or LAZ format. The LAS format is an industry standard for LiDAR data developed by
the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless
compressed version of LAS developed by Martin Isenburg (http://www.laszip.org/). The
data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data
are referenced vertically to the ellipsoid (either GRS80 or ITRF94), allowing for
the ability to apply the most up to date geoid model when transforming to orthometric
heights.